Leyden Jar:
A capacitor is a device made to store electrical charge. One of the simplest and earliest forms of a capacitor is the Leyden jar; this device was invented in 1745 by a Dutch Physicist named Peter Van Musschenbroek and Ewald Georg von Kleist. Originally, it was a glass jar that contained a fixed amount of water with a stopper. A nail or a wire would penetrate the stopper, one end touching the water and the other would be externally exposed. You would hold the jar with one hand and make the exposed wire come in contact with an electrical device. If you were to break this connection and touch the exposed end with your other hand, the current stored in the jar would flow, thus, causing an electrical shock. The Leyden jar is still very much used today in laboratories; however, they are somewhat different than the original version. The jar is coated inside and out with tinfoil and rather than having an exposed wire, there is a metal rod. The jar is often used for demonstrations or experiments.

Marcus Coates
References:
· "Leyden Jar." Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007. Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.
· http://reference.howstuffworks.com/leyden-jar-encyclopedia.htm
· Empires of Light: p. 23-27


Voltaic Pile:
The first battery was made in the late 1700’s by a man named, Luigi Galvani, also responsible for the galvanometer. In 1800, Alessandro Volta improved Luigi’s idea of the first battery. Volta’s battery consisted of three alternating layers. These layers consisted of the following: zinc, blotting paper soaked in saltwater, and silver. Volta’s arrangement of these materials was, and still is, known as the Voltaic Pile. The top and bottom layers of the pile must be different. By attaching a wire to the top and bottom, you will be able to measure a voltage. The difference in the top and bottom layer can be known as the positive and negative terminals of the battery.

Marcus Coates
References:
· http://electronics.howstuffworks.com/battery.htm
· "Alessandro Volta." Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007. Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.
· Empires of Light: p. 30-37


Dynamo:
A generator is used to convert mechanical energy into electrical energy; a device that converts electrical energy into mechanical is called a motor. One of the earlier names of the generator is the dynamo, which is short for dynamoelectric. If something dynamoelectric, then it is associated with the conversion of mechanical energy into electrical energy and vice-versa. It can also be called an alternator. The generator functions through electromagnetic means. In physics, it is known that electric currents can produce magnetic fields, as well as magnetic fields create electric currents. Applying this principle, the dynamo was born. An armature inside, wrapped in coils made of a conducting material, turns within a magnetic field. When this happens, the electric current produced by the magnetic field will travel through the conducting material, thus causing an output of electrical energy.

Marcus Coates
References:
· Easton, Elmer Charles. "Electric Motors and Generators." Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007. Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.
· http://reference.howstuffworks.com/electric-generator-encyclopedia.htm
· Empires of Light: p. 4


Transformer:
A transformers purpose is to change electrical energy. What that means is that it can change the strength of the current resistance, or voltage. For example, while driving along a highway, you often notice power lines. When you drive into a development, you can also notice a box at the top of the pole. This is the transformer. It is easier and cheaper to send electricity long distances at a high voltage; however, this voltage is much too dangerous to enter into your home. The transformer decreases the resistance in order to decrease the voltage. The reason is that the voltage is equivalent to the product of the current and the resistance. The amount of voltage that enters your house can vary depending on the country you live in. In the United States, the average voltage that enters your house is 120 volts. In South Korea, the voltage is 220 volts.

Marcus Coates
References:
· http://www.kropla.com/electric2.htm
· "Transformer." Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007. Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.
· http://reference.howstuffworks.com/transformer-encyclopedia.htm
· Empires of Light: p. 129-130


Arc Light:
Arc lights were once a solution to light the darkened streets. These lights were extremely bright and would illuminate every corner. However, they would emit an awful fume and would concern many people of the dangers. An Arc Light can be any light in which illuminated by means of a current leaping across a gap in a circuit. In 1809, a man by the name of “Sir Humphry,” demonstrated one of the very first Arc Lights (“Empires of Light”, page 35). He held in his hands two charcoal rods. One rod was connected to a strong Voltaic Pile. As the current began to flow through the first rod, Sir Humphry connected the second rod to it. Then he noticed that, from the glow of electrons, the current began to flow to the second rod. As he pulled the second rod further away, the light from the electrons grew more intense. As the electrons literally jump between the two carbon rods, they created a bright, blue glow that became severely bright. Thus, you have the Arc Light.

Marcus Coates
References:
· "Arc Lamp." Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007. Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.
· http://reference.howstuffworks.com/arc-light-encyclopedia.htm
· Empires of Light: p. 35

An AC motor is an electric motor that runs on alternating current. A drawback of the AC motor is the amount of current which must flow through the rotating contacts. Sparking and heating and those contacts can waste energy and shorten the lifespan of the motor. An AC motor consists of two basic parts; a stator and a rotor. The stator is an outside, stationary unit which has coils supplied with AC current used to produce rotating magnetic fields. The rotor is an interior mechanism connected to the output shaft. The rotor is given torque by the rotating field. There are two types of AC motors; synchronous and induction. The synchronous motor rotates at either the exact or a submultiple of the the supply frequency. The induction motor turns slower than the supply frequency and uses an induced current to create the maganetic field.

In 1882, inventor Nikola Tesla discovered the principle of the rotating magnetic field. Tesla later used this principle in his development of the two-phase induction motor in 1883. An electric motor converts electric power to mechanical power in it's rotor. An AC motor induces the power in the rotating device it uses. In a DC motor, the power is supplied directly from a DC source. The DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field used to generate power. Instead of coils, the DC motor gets it's magnetci field from exterior, high strength permanent magnets. The lower powered DC motor of Edison's was initially thought to be the better and safer of the two because of it's low power. Lower power than the AC motor meant lower risk. However, it was the ability of alternating current to remain useful over long distances that made it a favorite in the end.

Ryan Morris

www.solarbotics.net/starting/200111_dcmotor/200111_dcmotor2.html

Empires of Light: p. 97, 98, 132, 135

Incandescent Light Bulb:

The incandescent light bulb was the solution to in-home lighting. The development made it possible to light homes without the harmful polutions of other lighting methods. After a stuggle to find a proper filament, in 1879, Edison's team discovered that carbonized cotton thread would do the job. The first successful lighting lasted for 14 and 1/2 hours. They later replaced cotton thread with more efficient carbonized cardboard.

The light bulb has a basic structure. There are two contacts at the bottom which connect to the end of the electrical circuit. The contacts are attached to two wires that are then attached to the filament. The filament is in the middle of the bulb and is supported by a glass mount. These internal components are housed by a glass bulb. The bulb is filled with an inert gas, such as argon. When powered, an electric current flows between the contacts, wires an filament. This transfer of energy heats the atoms in the bulb. Metal atoms, when heated, release infarred photons which are visible to the human eye only when heated to at least 4,000 degrees farenheit.

Ryan Morris

www.home.howstuffworks.com/light-bulb1.html

Empires of Light: 62-71

Diode:

A diode is a very simple form of a semiconductor. That is, a diode has the capability to conduct electric current. It allows the flow of electricity in one direction, however, blocks it from flowing in the opposite direction. One may think of a diode as an electronic version of a check valve. Diodes are used in radio demodulation, power conversion, over-voltage protection, logic gates, ionizing radiation detectors, and temperature measuring.

Thermionic diode principles were originally discoverd by Frederik Guthrie in 1873. Karl Ferdinand Braun discovered the principle of operation of crystal diodes in 1874. Thomas Edison played a small part in diode development when he rediscovered the principle of thermionic diodes in 1880. Edison did not, however, develop his ideas any further.

Ryan Morris

www.kpsec.freeuk.com/page/Devices%3A

http://en.wikipedia.org/wiki/Diode

Transistor:

A transistor is also a semiconductor. Transistors are commonly used as amplifiers of electrically controlled switches. Transistors serve as the fundamental building blocks of the circuitry that governs the operation of computers, cellular phones, and all other modern electronical devices. Transistors can be used in both analog and digital functions because of it's fast response and accuracy. Some of these functions are amplification, switching, voltage regulation, signal modulation, and oscillators.

In 1928, German physicist Julius Edgar Lilienfeld registered the first three patents for the field-effect transistor principle. At Bell Labs, in 1947, the first pratical point-contact transistor was successfully built by William Shockley, John Bardeen, and Walter Brattain. Later in 1953, a solid-state radio reciever with four transistor was demonstrated at the Dusseldorf Radio Fair.

Ryan Morris

http://en.wikipedia.org/wiki/Transistor#History

http://nobelprize.org/educational_games/physics/transistor/history/